<!DOCTYPE html>
<style>
body {
  margin: 0px;
}

.scroller {
  overflow: scroll;
  width: 200px;
  height: 600px;
}

.box {
  background: rgba(0, 255, 0, 0.9);
  position: relative;
  width: 185px;
  height: 50px;
  top: 200px;
}

.indicator {
  position: absolute;
  width: 185px;
  height: 50px;
  background: red; /* covered up by .box when working */
}

.container {
  width: 100%;
  height: 1000px;
  background: grey;
}
</style>

<div id="scroller" class="scroller">
  <div class="container">
    <div class="indicator"></div>
    <div class="box"></div>
  </div>
</div>

<script>
  let scroller = document.getElementById('scroller');
  scroller.scrollTop = 200;
</script>
